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Ecosystems, material cycles and biodiversity - Science Year 10

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Introduction

Follow ecological connections, distinguish energy flow from material cycles, and evaluate biodiversity and restoration evidence with original data. Year 10 placement is editorial within the GCSE pathway.

Trace interdependence, food webs and trophic energy transfer

An ecosystem includes interacting organisms and their non-living surroundings. A population comprises organisms of one species in a defined area; a community includes the different populations living there. Abiotic factors include light, water availability, temperature and soil conditions. Biotic interactions include competition, feeding, disease and mutual relationships. A change can affect several linked populations, rather than acting on one isolated species only.

In a food web, state what the arrows mean. Our original meadow model uses an arrow from food resource to consumer, showing the direction of feeding transfer. Meadow plants supply leaves or seeds to different herbivores. The listed links are a simplified teaching network, separate from the more complex opening Commons illustration.

Food resource	Consumer receiving material and chemical energy
Meadow plants	Grasshopper
Meadow plants	Rabbit
Meadow plants	Mouse
Grasshopper	Frog
Frog	Owl
Mouse	Owl
Mouse	Fox
Rabbit	Fox

Follow two possible routes from meadow plants to owl: through grasshopper then frog, or through mouse. The fox also has two listed food resources, mouse and rabbit. If grasshoppers decline, frogs may lose food and owls may be affected, but the owl has an alternative pathway through mice. The network alone does not establish exactly how many owls will disappear or even the final numerical change once competition, timing and other resources are considered.

Interdependence extends beyond eating. Pollinators can support reproduction in flowering plants, plants can provide habitat and resources for other organisms, and decomposers connect dead material with nutrient availability. Competition can occur within a species as well as between species. A mutual relationship is not proof that every member of the community benefits from every change.

Original publisher: Amoeba Sisters, Food Webs and Energy Pyramids: Bedrocks of Biodiversity. Follow feeding transfers and the distinction between a network and an energy pyramid. Our meadow links and numerical budget are original models; the tasks remain usable without audio or the external player.

Energy transfer and material cycling need different explanations. Light energy can enter a system through photosynthetic producers, and chemical energy is transferred in feeding. At each trophic level, respiration and other processes dissipate energy to surroundings as heat, and not all material is eaten or incorporated into the next level’s new biomass. Energy is not recycled back into the Sun through decomposition.

Consider an original annual teaching account with the same area basis at each level. The numbers represent chemical energy stored in new biomass over the stated period, not organism counts or the standing biomass present on one day.

Trophic level	New-biomass energy / kJ m−2 year−1
Producers	10000
Primary consumers	1500
Secondary consumers	180

Primary-consumer production is fifteen percent of producer production, because 1500 divided by 10000 is 0.15. Secondary production is twelve percent of primary production, because 180 divided by 1500 is 0.12. These supplied transfers do not establish a universal ten-percent law. Across both steps, 180 is 1.8 percent of the original 10000; adding fifteen and twelve would not give the overall transfer percentage.

Track carbon, nutrients and water without double-counting

Matter moves between reservoirs and changes chemical form. Photosynthesis transfers carbon from carbon dioxide into organic compounds. Feeding passes organic material between organisms; respiration by plants, animals and many microorganisms returns carbon dioxide to surroundings. Dead organisms and waste provide resources for decomposers. Microbial respiration is part of the return pathway, not a separate source of newly created carbon atoms.

An original ecosystem-box account starts with one thousand carbon units stored inside the stated boundary. During one interval, photosynthesis imports one hundred and twenty units, total respiration exports ninety and another ten leave as exported organic material. The end store is 1020 units. The ninety already includes plant, animal and decomposer respiration; adding decomposer respiration again would double-count it. A net increase in this box is not proof that every ecosystem is always a carbon sink or that carbon has been permanently removed forever.

Combustion can move carbon from fuels or biomass into the atmosphere. Long-term stores, oceans, soils and living systems exchange carbon on different timescales. The course does not use old flux numbers as current measurements. A statement about storage needs a boundary, interval and evidence about both inputs and outputs; measuring one tree’s growth alone is not a complete global carbon budget.

Decomposition returns mineral nutrients from organic material to the environment, where producers may take them up again. Atmospheric nitrogen gas is not generally absorbed directly by plants as if it were nitrate in soil water. Nitrogen-fixing microorganisms can convert it into more biologically usable compounds. Decomposition can release ammonium; other microbial transformations produce forms such as nitrates available for plant uptake. Denitrifying processes can return nitrogen gas to the atmosphere. Follow the material forms rather than treating every arrow as photosynthesis.

Temperature, water availability and oxygen conditions affect decomposition and the organisms performing it. Aerobic decomposers require oxygen for their aerobic processes, but absence of oxygen does not mean every possible decomposition pathway stops. Waterlogged conditions can change rates, pathways and gases produced. These are ecological explanations, not instructions for growing unknown microbes.

Water evaporates from surfaces, plants release water vapour through transpiration, vapour can condense, and precipitation returns water to land and water bodies. Runoff, infiltration and groundwater movement connect stores. Sun-derived energy and gravity help drive these transfers. Land use, drainage, abstraction and pollution can alter where water is stored, how it moves and what quality is available, even while water continues to cycle.

Trace carbon and nitrogen through different forms, then distinguish material recycling from energy flow. Identify the roles of producers, consumers and microorganisms. Our separate 1000-to-1020 carbon account is original supplied data, not a measurement extracted from the animation. Original: Amoeba Sisters, Carbon and Nitrogen Cycles. The written explanations and native tasks work without sound or the external player.

Compare biodiversity, sample populations and evaluate restoration

Biodiversity is more than counting how many different names appear. Variation includes diversity within species, between species and among ecosystems. Species richness counts the species detected; relative abundance describes how individuals are distributed among them. Genetic variation and habitat differences add further dimensions. Use an appropriate measure for the question rather than treating one number as a complete verdict on an ecosystem.

The original equal-effort sample below records one hundred identified individuals in each habitat. P, Q, R and S represent four distinct taxa that are treated as species for this model. Both habitats have richness four, but the distributions differ.

Model taxon	Habitat A individuals	Habitat B individuals
Taxon P	40	97
Taxon Q	30	1
Taxon R	20	1
Taxon S	10	1

The most abundant species accounts for forty percent in A and ninety-seven percent in B. A is more even in this sample; saying B has more biodiversity simply because one species is numerous ignores the rest of the distribution. These observations do not establish the total number of species present but undetected, genetic diversity or an exact stability score. Different species’ roles and responses can affect resilience, so a simple richness count does not guarantee that one system will resist every disturbance better.

Sampling needs a defined area, method, effort and timing. In an original paper-only quadrat example, six non-overlapping 0.25-square-metre samples contain two, four, three, five, one and three target plants. Eighteen individuals across 1.5 square metres gives an estimated density of twelve per square metre. Extrapolating to a 120-square-metre plot gives an estimated 1440, subject to representativeness and spatial variation rather than an actual complete count.

$\hat{density} = \frac{2 + 4 + 3 + 5 + 1 + 3}{6 \times 0.25} = 12 i n d i v i d u a l s / m^{2}$

Random or appropriately stratified locations can support an area-wide estimate; a systematic transect may answer a different question about a gradient. Repeats across seasons and consistent identification help separate a biological change from altered detection or observer effort. Choosing only visually rich patches would bias the estimate upwards, and repeating the same unrepresentative patch does not fix that bias.

Human effects can include habitat loss and fragmentation, pollution, over-exploitation, climate-related shifts and impacts from some introduced species. Not every introduced organism becomes invasive. Excess nutrients can stimulate algal growth; subsequent respiration and microbial decomposition of organic material can deplete dissolved oxygen and affect aquatic animals. This is a causal sequence, not the claim that every fertiliser molecule directly poisons every fish.

Conservation can combine habitat protection and restoration, connectivity, reduced damaging inputs and carefully managed species or genetic resources. A seed bank complements living habitats rather than recreating an entire interacting ecosystem by itself. Management involves objectives, evidence, resources and possible trade-offs; a corridor or planting plan is not automatically successful because it looks green.

Use an original matched-monitoring illustration. Both areas have the same stated survey effort and comparable before/after intervals. Values are mean detected pollinator-species richness per standard survey, not real national indicator data.

Survey area	Before: mean detected richness	After: mean detected richness
Matched reference area	6	7
Restoration area	5	9

The reference changes from six to seven, a rise of one; the restoration area changes from five to nine, a rise of four. The difference in changes is three detected species per standard survey. This is a more informative comparison than attributing the entire rise of four to restoration, but it still does not prove causality without considering baseline differences, weather, wider land use, replication and detectability.

For real England trends, consult dated official indicators with their methods and uncertainty, including habitat condition, abundance and distribution measures. Our fictional numbers are not a claim about current national progress. A strong ecological conclusion identifies its evidence, timescale and limits and proposes a monitoring plan that could reveal both success and unintended effects.

Interactive Tasks

Quiz: Test Your Knowledge

Which account distinguishes an ecosystem from a population? (An ecosystem includes interacting communities and non-living surroundings, while a population is one species in a defined area) (!An ecosystem contains only one individual animal) (!A population always includes all species and all soil chemistry) (!Both terms mean only the energy stored in predators)

What do arrows in our original meadow feeding table mean? (Food resource to consumer receiving material and chemical energy) (!Predator always pointing to the prey it chases) (!Every possible movement of water through soil) (!A guarantee of the exact size of a future population change)

Why does a grasshopper decline not determine an exact owl decline from this network alone? (The owl has a mouse pathway and wider interactions and timings are not quantified) (!The network proves owls never depend on frogs) (!Arrows create new food automatically) (!Every population must change by exactly the same percentage)

What are the two successive energy-transfer percentages in the supplied annual account? (Fifteen percent then twelve percent, with 1.8 percent overall) (!Ten percent at every step by definition) (!Twenty-seven percent overall because fifteen and twelve must be added) (!One hundred percent because all chemical energy cycles back to producers)

What is the final carbon store in our stated box? (1020 units, without adding decomposer respiration a second time) (!1110 units because respiration never removes carbon) (!930 units because photosynthesis is an output) (!Zero because all carbon is destroyed during respiration)

Which statement about nutrient cycling is appropriate? (Microbial transformations change nitrogen forms, while energy is not recycled in the same way) (!Plants normally turn atmospheric nitrogen gas directly into sunlight) (!Every nutrient arrow is the same as photosynthesis) (!Oxygen absence stops every possible decomposition pathway)

How do the two original habitat samples compare? (Both have richness four, but A is more even and B is dominated by one species) (!B has richness ninety-seven because its largest count is ninety-seven) (!A has no biodiversity because its counts differ) (!Identical richness proves identical stability under every disturbance)

What estimated density follows from the six supplied quadrats? (Twelve target individuals per square metre) (!Eighteen target individuals per square centimetre) (!Three target individuals in the entire 120-square-metre plot) (!One thousand four hundred and forty individuals per quadrat)

What is the difference in before/after richness changes between restoration and reference? (Three detected species per standard survey, with causal limits) (!Four, with proof that restoration caused every change) (!Nine, because only the final restoration value matters) (!Minus one, because comparison intervals must be ignored)

Which conservation conclusion is best supported? (Use multiple appropriate measures, matched monitoring and contextual evidence rather than a single guaranteed-success number) (!Every introduced species is invasive) (!A seed bank completely replaces all ecosystem interactions) (!A green-looking intervention needs no follow-up measurements)

Memory Game

Population	Organisms of one species in a defined area
Community	Interacting populations of different species in an area
Abiotic factor	A non-living environmental condition influencing organisms
Species richness	The number of species detected under a stated method
Relative abundance	How individuals are distributed among the recorded species
Decomposer	An organism breaking down organic material and contributing to material recycling

Drag and Drop

A food resource supplies a consumer in our original model	Draw the teaching arrow from resource towards consumer
Respiration releases energy to surroundings as heat	Distinguish energy dissipation from nutrient recycling
Total respiration already includes decomposer respiration	Do not subtract that same carbon flow twice
Four recorded species have counts ninety-seven, one, one and one	Separate richness four from strong dominance by one species
A restoration area and reference both improve over the interval	Compare changes and investigate other influences before claiming causality

Crossword Puzzle

ECOSYSTEM	What term combines a community with its interacting non-living surroundings?
POPULATION	What group comprises one species in a defined area?
ABIOTIC	What adjective describes a non-living environmental factor?
RICHNESS	What measure counts the species detected?
TRANSPIRATION	What plant process releases water vapour to the atmosphere?
DECOMPOSER	What organism breaks down dead organic material and contributes to nutrient cycling?

LearningApps

Optional extra practice. Choose an appropriate activity with your teacher. If the external collection is unavailable, use the native activities and independent tasks in this course.

Cloze Text

Open Tasks

Easy

Read an ecological arrow: Explain resource-to-consumer direction in the original meadow network and distinguish it from the opening diagram’s broader key.
Name interactions: Compare feeding, competition, pollination and decomposition with abiotic influences.
Trace a material pathway: Follow carbon through photosynthesis, feeding, respiration and decomposition without creating carbon atoms.
Compare richness and dominance: Explain how both original habitats can contain four recorded species but have different distributions.

Standard

Calculate energy transfers: Calculate both successive percentages and the overall two-step percentage using the stated new-biomass energy basis.
Balance the carbon box: Check the end store and explain why decomposer respiration is not counted again.
Estimate a population: Calculate sampled area, density and the qualified whole-plot estimate from the six original quadrats.
Analyse restoration changes: Calculate both changes and their difference, then explain why the comparison is more useful than the final restoration number alone.

Advanced

Evaluate a cascade claim: Use alternative feeding pathways, competition and timing to challenge a precise population forecast from the network alone.
Design a stronger monitoring plan: Choose appropriate random, stratified or gradient sampling and consider seasons, detectability, observer consistency and replication.
Explain nutrient-pollution effects: Build a causal chain through excess nutrients, increased organic production, respiration/decomposition and oxygen depletion, avoiding a universal direct-poison claim.
Judge conservation evidence: Combine richness, abundance, habitat condition, genetic resources and management trade-offs; distinguish our invented data from dated official England indicators.

Learning Check

Interdependence model: Name arrow direction and preserve uncertainty.
Energy account: Use the same area and interval basis at every level.
Carbon, nutrients and water: Separate reservoirs, chemical forms and energy.
Abundance and sampling: Report what the sample establishes and what it does not.
Restoration comparison: Compare changes before making causal claims.
Environmental change and management: Connect mechanisms with a monitoring plan.

Worked checks and assessment guidance

The original feeding arrows run from meadow plants to grasshopper, rabbit and mouse, onward from grasshopper to frog, and from frog or mouse to owl; mouse and rabbit also supply fox. An owl therefore has alternative listed feeding routes. Grasshopper decline could have wider effects but does not set an exact owl count. Competition, pollination, decomposers and abiotic conditions add interactions beyond the simplified feeding links.
New-biomass energy is 10000, 1500 and 180 kJ per square metre per year. The first transfer is 1500 divided by 10000 times one hundred, or fifteen percent; the second is 180 divided by 1500 times one hundred, or twelve percent. Overall 180 divided by 10000 gives 1.8 percent. The successive fractions multiply, not add. These are supplied model values, not a universal ten-percent law or a count of organisms.
The box store becomes 1000 plus 120 minus 90 minus 10 equals 1020 carbon units. Total respiration already includes decomposers, so subtracting them again double-counts a flow. Carbon and nitrogen change forms among reservoirs; microbial transformations make nitrogen available and return forms to the atmosphere. Water moves among stores through evaporation, transpiration, condensation, precipitation and other pathways. Energy dissipates rather than cycling back like mineral matter.
Both habitats record four species and one hundred individuals, so richness is four in each sample. Their largest shares are forty and ninety-seven percent; A is more even. The six quadrats total eighteen target plants across 1.5 square metres, giving twelve per square metre and an extrapolated 1440 over 120 square metres if representative. These are estimates and sample distributions, not a complete species inventory, genetic-diversity measurement or exact stability score.
The matched reference rises from six to seven, or plus one, while restoration rises from five to nine, or plus four. The difference in changes is plus three detected species per standard survey. This adjusts for the shared reference change in a simple comparison, but baseline differences, weather, surrounding land use, replication and detection still need consideration. The fictional values do not report national England trends.
Habitat fragmentation, pollution, climate change and some invasive introductions can alter communities. Nutrient enrichment can support blooms and subsequent oxygen depletion through respiration and decomposition. Conservation may combine protection, restoration, connectivity and reduced damaging inputs, with genetic collections as complements. Evaluate habitat condition, abundance, distribution, species roles and unintended effects over an appropriate interval rather than declaring success from one rich-looking patch.

Learning evidence

Retain the original feeding network, energy-transfer calculations, checked carbon budget, richness-and-abundance comparison, quadrat estimate and restoration difference-in-changes critique. State sampling limits, causal assumptions, timescales and the difference between fictional models and official monitoring.

OER and Wikipedia

Original meadow links, annual new-biomass energy account, bounded carbon ledger, habitat counts, quadrat example, restoration-monitoring data, tasks and worked feedback. The unchanged Thompsma/Pixelsquid ecosystem and j4p4n/NASA-based water-cycle originals were visually inspected and byte-checked. A separate older carbon-flux diagram was excluded because its numbers should not be mistaken for current estimates. Both original Amoeba Sisters video previews, publisher identities and playable embeddings were checked.

DfE GCSE combined science, ecosystem and environmental-change scope. NOAA: Carbon cycle, reservoir and process context; USGS: Water cycle, stores, transfers and human influences. Convention on Biological Diversity: Article 2, dimensions of biodiversity and ecosystem definitions, paraphrased. US EPA: Nutrient pollution, enrichment and oxygen-depletion context. Defra: England biodiversity indicators, dated habitat, abundance and distribution reporting; no national trend values are copied into our invented datasets. Sources consulted 13 November 2026.

FoodWeb.svg, Original: Thompsma Vector: Pixelsquid, CC0. Unchanged original; caption and learning activities are original.

Water cycle.svg, j4p4n (NASA Precipitation Measurement Missions), Public domain. Unchanged original; caption and learning activities are original.

Additional original video: Food Webs and Energy Pyramids: Bedrocks of Biodiversity, Amoeba Sisters; native publisher embedding.